How thin is too thin? Well, the Chinese smartphone makers are always pushing their limits on this end. Following Gionee's 5.1mm Elife S5.1 and Oppo's 4.85mm R5, today Vivo has set a new record with its X5Max, a 4.75mm-thick Android phone that still manages to pack a number of notable features. The slim aluminum mid-frame houses a vibrant 5.5-inch 1080p Super AMOLED screen, a 1.7mm-thick logic board and a 5-megapixel f/2.4 front camera. Flip to the back and you'll find a 13-megapixel f/2.0 main camera -- the inevitable bulge that goes beyond the phone's official thickness by almost 2mm -- and a loudspeaker towards the bottom. On the whole, the phone feels surprisingly light (Vivo has yet to list the official weight) but also solid and well-made.